The woman, identified only as Miss X, told the town hall she was at risk and needed to be moved into temporary accommodation.
Though the alleged attacker did not live with her, he knew her address.
Waltham Forest said she was eligible to be moved and in “priority need” but did not offer her any alternative housing until “several months” afterwards, the Housing Ombudsman said in a report.
Miss X declined the offer as it was in a state of disrepair, and the ombudsman said the council was at fault for not first checking the condition of the property.
The ombudsman, which acts as a mediator between local authorities and residents with complaints, said it was also at fault for not sorting her a room in a hotel, which it would have paid for on a nightly basis.
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There is a substantial shortage of housing in the borough, the council says, but local authorities are required to house those they owe a “relief duty”.
While Waltham Forest was assessing its own housing supply, Miss X found two privately-rented flats the council said they would pay the deposit and first month’s rent for.
Though both properties were affordable for the town hall, they were let out to other tenants while her requests were being processed and she missed both windows.
The ombudsman said: “There are many factors involved in deciding who a private property is let to and we cannot know whether Miss X would have secured those tenancies if the council had provided Miss X with the funds more quickly.
“However I have recommended a service improvement in relation to this, due to the likelihood of injustice being caused to others by the length of time the council is taking to consider these requests.”
The town hall was ordered to pay Miss X £3,050 compensation for the 14 months she spent at home, including the 11 where she had not been informed she could bid for homes on the housing register.
Deputy council leader Ahsan Khan, who also serves as the cabinet member for housing, said the town hall “did not meet her expectations”.
He said in a statement: “Everyone has the right to feel safe and secure in their home – we know how difficult the situation is for anyone experiencing domestic abuse. Our teams work hard to assist anyone at risk who approaches us for help.
“We apologise to the resident for the poor service they received in this case. We know that we did not meet their expectations and we have actioned the ombudsman’s recommendations, including paying compensation to the resident for the distress caused and assisting them to find a suitable property.
“We are also updating the way we work so that the process of helping residents with rent and a deposit for the fast-paced private rental market is quicker and at the same time improving how we communicate important information in a timely manner.”
In February last year, Waltham Forest was slapped with £18,800 in fines over three cases of severe maladministration.
The cases involved the council failing to address individual issues with damp, mould and antisocial behaviour in its social housing.
